High-power optical fiber beam combining laser output head

Abstract

The utility model belongs to the field of optical fiber laser, particularly relates to a high-power optical fiber beam combining laser output head, and simultaneously solves the beam combining problem of a high-power optical fiber output laser and the laser damage problem of an output end face caused by high energy density of high-power laser. The high-power optical fiber beam combining laser output head is an optical fiber light cone which is formed by drawing a plurality of optical fiber thin rods, and the small end face of the optical fiber light cone is provided with scattered tail fibers. The taper of the light cone is (2-20): 1; and the diameter of the large end surface is 2mm-30mm. The device is convenient and flexible, simple to install and debug and low in cost.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber lasers, and specifically relates to a high-power optical fiber beam-combining laser output head, which simultaneously solves the beam-combining problem of high-power optical fiber output lasers and the problem of output end face laser damage caused by high energy density of high-power lasers. Background Art

[0002] Due to the advantages of high brightness, monochromaticity, directionality and coherence, lasers have developed rapidly and are widely used in actual production. However, during large-scale production, the high energy density of high-power lasers and the low laser damage threshold of conventional output heads have been exposed. Therefore, a new type of high-power fiber beam-combining laser output head that is convenient and flexible to use, has a high laser damage threshold, and can effectively reduce the internal energy density needs to be studied urgently.

[0003] Due to its high power level, high-power fiber lasers are generally designed to have a thicker core than conventional fiber cores in order to reduce the laser power density in the single-mode fiber core to ensure high-quality output. The same is true for high-power fiber beam-combining laser output heads. However, such a design of the fiber light cone will increase the spacing between the fiber filaments in the fiber light cone and the spacing between adjacent fibers, resulting in uneven output light at the output end and increasing the difficulty of subsequent optical path design. Using the fiber light cone as a high-power fiber beam-combining laser output head can effectively increase the laser mode field area at the output end of the output head, effectively reduce the internal energy density and largely avoid the influence of the thermal lens effect.

[0004] Fiber tapers are widely used in visible light display panels and laser output port couplers due to their good transmission wavelength range and high transmittance, but there are few reports on laser beam combiner output heads. At present, fiber tapers have been successfully prepared (China Patent CN1349110A, Cen Dagong; Liu Dakang; Li Benqiang; Wei Yi, Fiber Taper Drawing Technology and Equipment), and fiber tapers can be used to enhance the coupling of light sources and have been successfully applied (China Patent CN102882128B, Wang Yanhong; Zhou Hanchang; Gao Wenhong, High-power and high-brightness laser light source based on fiber taper coupling), indicating that fiber tapers can be used for laser output ports.

[0005] In order to solve the problems of high energy density and uneven output light at the output end of the conventional laser beam combining output head, the present invention proposes to use regular hexagonal optical fiber rods to draw optical fiber light cones, shorten the distance between adjacent optical fibers, make the output light at the output end more uniform, and facilitate subsequent optical path design. The present invention is flexible and simple and can effectively perform laser beam combining output. Summary of the invention

[0006] In order to solve the problem of high laser energy density and low laser damage threshold of conventional output coupling devices in the existing high-power laser processing process and realize the combined output of several lasers, a high-power fiber beam-combining laser output head and its manufacturing process are provided.

[0007] The present invention is realized by the following technical scheme: a high-power optical fiber beam-combining laser output head, which is formed by drawing a plurality of optical fiber thin rods and has an optical fiber light cone with a scattered fiber pigtail (202) on the small end face; a single high-power optical fiber beam-combining laser output head can have scattered fiber pigtails (202) of different sizes, the scattered fiber pigtails (202) are commercial laser optical fibers, the sizes of the scattered fiber pigtails (202) are 105 / 125, 20 / 400, 25 / 400, 50 / 400, 100 / 360, 200 / 220, 400 / 440, the scattered fiber pigtails (202) on one side of the small end face (203) are scattered in the form of single filaments, each scattered fiber pigtail can be coupled to a laser light source through a connector, the laser emitted by the high-power laser is coupled to the scattered fiber pigtails through the connector and incident into the scattered fiber pigtails, and enters the inside of the optical fiber light cone, and then output through the large end face 201 of the optical fiber light cone. The fiber light cone dispersion pigtail can be spatially coupled with a commercial rod collimating lens C-lens or G-lens and a commercial laser of the corresponding working band, or coupled with a commercial laser fiber to be connected to the optical path. The diameter of the small end face 203 of the light cone is 400μm-1mm, the diameter of the large end face 201 is 2-30mm, and the taper, that is, the ratio of the large end face to the small end face diameter is 2~20:1.

[0008] The small end face 203 of the present invention can be drawn very small and can be coupled with most high-power lasers; the large end face 201 can be prepared to be larger, which is beneficial to the heat dissipation of the light cone and effectively avoids the thermal lens effect. At the same time, because its output end cross-section (i.e., large cross-section) has a large diameter, the final output laser energy density can be effectively increased after subsequent optical path design.

[0009] The present invention uses an optical fiber light cone with a dispersed pigtail 202 on the side of the input end face (i.e., the small end face 203 of the optical fiber light cone). When working, the high-energy laser of the high-power laser can be dispersed into each pigtail, and then output from the output end face (i.e., the large end face 201) to the subsequent optical path. The output end face is an optical end face with a transmittance greater than 90% in the range of 400-2500nm, and is plated with a commercial anti-reflection film of the corresponding working wavelength by a magnetron sputtering method. In this way, the heat dissipation performance of the light cone is improved, and efficient coupling of the light cone is achieved.

[0010] The advantages of the present invention are small size, convenience and flexibility, simple installation and debugging, low cost and simple preparation; it solves the problems of high energy density of lasers and low laser damage threshold of conventional output coupling devices, while effectively avoiding the thermal lens effect in the light cone, and can be widely used in industrial high-power laser processing, laser lighting systems and other fields.

[0011] To achieve the above solution, the technical solution of the present invention is as follows:

[0012] A high-power fiber beam combining laser output head preparation process comprises the following steps:

[0013] Optical fiber drawing step: drawing an optical fiber preform having an optical fiber core and an optical fiber cladding structure into a hexagonal optical fiber thin rod having a length greater than 50 mm and an inscribed circle diameter of 1-2 mm, the implementation scheme of which is as follows:

[0014] The fiber is drawn in a special fiber drawing tower, with the drawing temperature of the fiber thin rod being 800±1℃, the feeding speed being 3.3-5.5mm / min, and the drawing speed being 10-60mm / min.

[0015] The light cone preform preparation steps are as follows: a certain number of optical fiber rods are closely arranged into an optical fiber rod array according to a honeycomb regular hexagonal structure, a position A 1-5 mm away from one end and a position B 10-20 mm away from the end are respectively bound and fixed with high temperature resistant materials, and each optical fiber rod is separated at the other end C of the optical fiber rod by utilizing the flexibility of the optical fiber rod to form a light cone preform;

[0016] The preparation steps for optical cone drawing are as follows: the optical fiber rod array, which is bound and fixed with high temperature resistant materials, is vertically placed from the middle part of position A to position C in a high temperature heating furnace of a drawing tower with segmented optical fiber taper drawing function, and the position A, position B and position C of each thin rod are respectively fixed with the top fixing fixture a, the taper fixture b and a plurality of drawing fixtures c;

[0017] Light cone drawing step: by accurately controlling the temperature of the AB position and the BC position of the optical fiber rod array bound and fixed by high temperature resistant materials, and controlling the different drawing rates of the taper drawing fixture b and the drawing fixture c, a fiber light cone with a certain taper ratio is formed at the AB position, and the optical fiber rod at the BC position is drawn into a certain number of scattered optical fiber filaments with a required diameter. By controlling the drawing speed of different drawing fixtures c respectively, the cladding thickness of each single fiber core after drawing can be the same or different. The implementation plan is as follows:

[0018] The uneven heating temperature field of light cone drawing will inevitably lead to the existence of temperature gradient of the heated body. In order to prevent the light cone preform from bursting due to temperature imbalance during the taper drawing process, it is heated together with the furnace at a heating rate of 0.7 ℃ / min. Finally, it is heated to 680 ℃ after nearly 21 hours; then maintained at 680 ℃ for 3 hours to keep the internal temperature of the preform consistent; then heated to 750 ℃ ​​at a heating rate of 0.65 ℃ / min and maintained for 3 hours, and then the taper drawing operation is started using a homemade taper drawing machine, using a pulling force of 70-80kg.

[0019] Light cone annealing step: After the taper drawing step is completed, it cannot be cooled directly with air, otherwise the light cone will deform or even burst due to internal stress, and the annealing process can effectively release the internal stress in the light cone. The light cone drawn by the taper drawing machine is quickly transferred to a muffle furnace that has been heated to 680°C, and annealed at a cooling rate of 0.7°C / min to 620°C for 30 hours.

[0020] Light cone cooling process: After annealing, it is not advisable to cool directly with air, as the surface of the light cone will crack due to the large temperature difference. After annealing, continue to cool in the muffle furnace at a cooling rate of 0.01℃ / min to 560℃, then cool at a cooling rate of 0.05℃ / min to 400℃, and then cool at a cooling rate of 0.2℃ / min to 40℃, and take out the light cone.

[0021] Scattered pigtail coating step: Each optical fiber filament drawn out of the BC section is coated separately, so that the optical fiber filament has better toughness and strength, and finally a high-power optical fiber beam combining laser output head with excellent performance is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the preparation steps for light cone drawing;

[0023] Figure 2 This is a schematic diagram of the structure of a high-power fiber beam-combining laser output head;

[0024] Figure 3 It is the arrangement of thin optical fiber rods;

[0025] In the figure, 201 is the large end face of the optical fiber light cone, 202 is the scattered pigtail, and 203 is the small end face of the optical fiber light cone.

Claims

1. A high-power fiber beam combining laser output head, characterized in that: The optical fiber light cone is drawn from several thin optical fiber rods. The small end face of the optical fiber light cone has a scattered fiber pigtail. Each scattered fiber pigtail can be coupled with a high-power laser. The laser emitted by the high-power laser is coupled with the scattered fiber pigtail and incident on the scattered fiber pigtail, thereby entering the interior of the optical fiber light cone and then output through the large end face of the optical fiber light cone. The transmitted laser power is greater than 500W high-power laser.

2. A high-power fiber beam combining laser output head according to claim 1, characterized in that: The diameter of the large end face (201) of the optical fiber light cone is 2-30 mm, and the taper, i.e., the ratio of the diameter of the large end face (201) to the diameter of the small end face (203), is 2-20:

1.

3. A high-power fiber beam combining laser output head according to claim 1, characterized in that: One side of the large end face (201) of the optical fiber light cone is ground and polished into a high-transmittance optical end face, and is coated with an anti-reflection film with a high damage threshold at a corresponding working wavelength.

4. A high-power fiber beam combining laser output head according to claim 1, characterized in that: Each optical fiber of the dispersed pigtail (202) on one side of the optical fiber light cone small end face (203) is directly fused with a rod-shaped collimating lens C-lens or G-lens, and can be spatially optically coupled with a laser, or each dispersed pigtail (202) can be directly optically fused coupled with a laser light source.

5. The high-power fiber beam combining laser output head according to claim 1, characterized in that: The cross section of the cladding of the optical fiber thin rod used for drawing the optical fiber light cone is a regular hexagonal honeycomb structure, which is closely arranged without gaps.

6. A high-power fiber beam combining laser output head according to claim 1, characterized in that: The size of each optical fiber light cone fiber pigtail (202) is variable, and the size of each pigtail (202) is one or more of 105 / 125, 20 / 400, 25 / 400, 50 / 400, 100 / 360, 200 / 220, 400 / 440, so as to facilitate coupling with the laser optical fiber.

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